"We must refrain from everything that can deteriorate the situation further," Steinmeier said after a meeting with Russian Foreign Minister Sergei Lavrov.
The German official said Berlin was concerned about the situation in Crimea and there was no complete clarity on the developments in the region as the results of investigations by Ukrainian and Russian sides were expected.
"We do not have specific information, there is totally contradictory data from Russian and Ukrainian sides," the German foreign minister added.
On Wednesday, Russia's Federal Security Service (FSB) said that it had eliminated a spy ring organized by the Ukrainian Defense Ministry in Crimea, detaining both Russian and Ukrainian nationals involved in preparing terrorist attacks on the peninsula. An FSB officer died as a result of a firefight during the arrest.
The Federal Security Service also said it had prevented two overnight attempts by Kiev-organized terrorist groups from entering Crimea overnight into August 8, in which one Russian soldier was killed.